Security is being tightened at UK airports following fears from the US of increased terrorist threat levels.

The security threat level remains at ‘substantial’, meaning that an attack is a strong possibility. The changes come after the White House voiced fears that terrorists were planning to bring down a plane with help from radicalised European jihadists returning from Syria.

President Barack Obama told American TV news channel ABC: “They’ve got European passports. They don’t need a visa to get into the United States”.

The Department of Transport has issued a statement confirming increased security, but would not provide further information on the details of this.

“We have taken the decision to step up some of our aviation security measures,” it said.

“For obvious reasons we will not be commenting in detail on those changes.”

The majority of passengers should not experience significant disruption, but travellers to the US should arrive earlier to allow for any additional time it takes to get through the extra security checks.

“The safety and security of the public is our paramount concern. The UK has some of the most robust aviation security measures and we will continue to take all the steps necessary to ensure that public safety is maintained,” added the Department of Transport.

The Department of Homeland Security said changes to aviation security in the US would be made in the “upcoming days”. Airlines have responded to say they are ready to bring in any new security measures when instructed.

The current scanners show a ghost-like outline of the body produced by low doses of x-rays. In line withlegislation from Brussels, the new scanners will scan passengers using radio frequency-based millimetre wave technology. Instead of airport security being able to see the scans, a computer will analyse them and produce a stick figure diagram indicating where staff should search for hidden objects.

The new system might give more privacy on the images the scanners produce, but it does potentially bring back frisking by airport staff, something which has left many perplexed.

Andrew Harrison, Chief Operating Officer at M.A.G, Manchester Airport‘s parent company commented: “We’re baffled by this situation because health experts say they are safe plus the overwhelming majority of our passengers and security staff prefer body scanners to frisking and it’s frustrating that Brussels has allowed this successful trial to end.”

“Our security surveys and those run by the Department for Transport show passengers regularly rate their experience at Manchester as one of the best security processes in the UK if not Europe.

“There’s no doubt that body scanners play a big part in these results. That’s why we are once again investing in new next generation scanner technology where the human examination of images is automated.”

The trial of the new five security scanners is expected to last three months.

Ministers are calling for the Home Office to relax security checks at airports and to revert back to the risk-based checks abandoned last year. The ministers say that long queues at UK airports are damaging the travel industry and could harm the wider economy.

Although more staff have been recruited for the period during the Olympics, the cross-party Home Affairs Select Committee said they fear waiting times will increase again afterwards as staff will be cut back again yet there will be more foreign students arriving in the UK for the new academic year, impacting on waiting times once again.

The risk-based checks mean that security staff could wave through low-risk groups such as groups of school children and families with children. However, this strategy was stopped last year as it was found that security staff had relaxed the rules further than had been intended, and without authorisation. The Select Committee called for the reintroduction of the checks, claiming in a report that it had been effective in handling large groups, and to add “smart zones” to screen passengers before they arrive in the UK so that any individuals deemed to present a risk could be subjected to further checks.

A further measure suggested to help passengers feel more informed about waiting times, is for boards with the approximate waiting time to be installed at security and immigration, similar to those currently at Heathrow T4.